This invention relates to a device that may be attached to a head positioning unit to indicate the orientation at which the head should be maintained for effective cephalometric radiography.
In the field of orthodontics, analysis of the skeletal and tooth structure is made from X-ray photographs that are taken laterally of the face. For each set of X-rays, the head must be positioned and oriented identically in order to provide a basis upon which to determine the type of treatment necessary or the improvement that is being made during the course of treatment. Accurate comparison between the different sets of X-ray photographs can then be made and any changes in the skeletal structure can be readily ascertained. The cephalometer mechanisms which are used to position the head typically include a pair of vertical ear posts which contact opposite sides of the head to locate it properly between the X-ray machine and the cassette which contains the X-ray sensitive film.
It is also necessary to provide a means for repeatably orienting the head at the proper tilt angle with respect to horizontal. Ordinarily, the porion or ear canal and the infra-orbital notch area at the bottom of the orbital canal should be in the same horizontal plane, which is commonly known as the Frankfort plane. The ear posts usually have small rods or pins which fit into the ears, and a pointer device is provided to indicate the proper position of the orbital area for correct orientation of the head. The pointer is carried on a support arm which attaches to the main superstructure of the head holder in a manner to fold or telescope down such that the pointer is at the same elevation as the ear pins. When the head is oriented with the orbital area at the same elevation as the pointer, proper tilting of the head is established.
Even though this conventional pointer assembly has been widely used, it has not been entirely satisfactory in many respects. If the pointer remains in its down or indicating position to assure that the head remains in the proper orientation during the X-ray process, it shows up in the X-ray photograph at a location where it can obscure important areas of the skeletal structure. Moreover, the pointer is mounted to the main superstructure of the head holder, and it therefore requires a complicated mounting assembly which allows it to be folded or telescoped up and down. Manifestly, this adds substantially to the complexity and expense of the device, while increasing the time and difficulty involved in properly positioning the head.
In view of these deficiencies in the conventional pointer mechanism, it is the primary goal of the present invention to provide an improved device for indicating the orientation at which the head should be maintained during the cephalometric X-ray process.
More specifically, it is an object of the invention to provide a device of the character described which is adapted to be attached directly to the ear posts of existing head positioning mechanisms in order to avoid the expense and complexity of an additional mounting assembly.
Another object of the invention is to provide a device of the character described which may be pivotally attached to the ear post in order to be quickly and easily moved into and out of indicating position.
Still another object of the invention is to provide a device of the character described which may be attached to a wide variety of existing head positioning mechanisms.
A further object of the invention is to provide a device of the character described which provides a permanent mark of the Frankfort plane on the X-ray film and which does not obscure any important areas of the film. Since the indicating device comprises a small diameter wire which is located entirely in the horizontal Frankfort plane, it may be left in place to provide a single straight line which indicates the Frankfort plane on the X-ray film. Alternatively, the wire may be pivoted to a retracted position near the rear of the skull where the bone structure is not important from an orthodontic standpoint.
An additional object of the invention is to provide a device of the character described which is simple and economical to construct and safe and accurate in use.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.